Utility sheds are necessary for lawn and garden care, as well as general all-around home storage space. Typically, items such as garden tractors, snow blowers, tillers, ATVs, motorcycles, lawn tools and the like are stored within utility sheds for the convenience of the homeowner.
The prior art has proposed a number of different panel systems, or kits, comprising blow molded and/or extruded panels which are combined with connector members for forming storage structures, e.g. utility sheds. Unfortunately, blow molding and/or extrusion of panels for utility sheds has resulted in shortcomings within the state of the art products. For example, due to the nature of the manufacturing process, blow molded and/or extruded plastic components cannot be formed with the intricate shapes and/or sharp corners required for integrated connectors. Therefore, these systems require extruded metal or plastic connector members having a specific cross-sectional geometry that facilitates an engagement between the blow molded or extruded panels to complete the structure.
A particularly common structure for the connector members is one having an I-beam cross section. The I-beam defines free edge portions of the connector member which fit within appropriately dimensioned and located slots in the panel members. U.S. Pat. No. D-371,208 teaches a corner extrusion for a building sidewall that is representative of the state of the art I-beam connector members. The I-beam sides of the connector engage with the peripheral edge channels of a respective panel and thereby serve to join such panels together at right angles. Straight or in-line versions of the connector members are also included in the kits to join panels in a coplanar relationship to create walls of varying length.
Another drawback associated with blow molded panels is the requirement of an inner and an outer wall. The inner and outer walls are a necessary product of the blow molding manufacturing process. While the inner wall may add some rigidity to the panels, it also adds a significant amount of weight and dramatically increases the volume of plastic necessary to form a panel of a given size when compared to other methods of manufacturing, such as injection molding.
A further drawback associated with blow molded panels relates to accurate control of wall thickness throughout the panels. The blow molding process does not allow the wall thickness of the panels to be accurately controlled. Once the molten plastic is conveyed to the tooling, there is minimal control over where the plastic flows during formation of the panel. Also, the blow molding process does not allow the intentional formation of thick and thin sections within a single panel for engineered rigidity at the points of high stress or high load concentration.
Extruded panels generally require hollow longitudinal conduits for strength. Due to the nature of the manufacturing process, the conduits are difficult to extrude in long sections for structural panels. Thus, they also require connectors to achieve adequate length for utility shed roofs. A common structure for connecting extruded members has a center I-beam with upper and lower protrusions for engaging the conduits. Wall panels utilizing these connectors are vulnerable to buckling under loads and may have an aesthetically unpleasing appearance. Moreover, roof loads from snow and the like may cause such walls to bow outwardly due to the clearances required between the connectors and the internal bores of the conduits. U.S. Pat. No. 6,250,022 discloses an extendable shed utilizing side wall connector members representing the state of the art. The connectors have a center strip with hollow protrusions extending from its upper and lower surfaces along its length; the protrusions being situated to slidably engage the conduits located in the side panel sections to create the height needed for utility shed walls.
The aforementioned systems can also incorporate roof and floor panels to form a freestanding enclosed structure such as a small utility shed. U.S. Pat. Nos. 3,866,381; 5,036,634; and 4,557,091 disclose various systems having inter-fitting panel and connector components. Such prior art systems, while working well, have not met all of the needs of consumers to provide the structural integrity required to construct larger sized structures.
Larger structures must perform differently than small structures. Large structures must withstand increased wind and snow loads when compared to smaller structures. Paramount to achieving these needs is a panel system which eliminates the need for extruded connectors to create enclosure walls which resist panel separation, buckling, and racking. A further problem is that the wall formed by the panels must tie into the roof and floor in such a way as to unify the entire enclosure. Also, from a structural standpoint, the enclosure should include components capable of withstanding the increased wind, snow, and storage loads required by large structures.
Therefore, what is needed in the art is an injection molded modular roof system for utility enclosures. The modular roof system should achieve objectives such as light weight single wall construction. The construction of the panels should eliminate the need for extruded I-beam connectors to create a roof assembly which resists panel separation, buckling, and racking. The roof assembly should be capable of withstanding the wind and snow loads typically associated with utility enclosure roofs.
There are also commercial considerations that must be satisfied by any viable utility shed enclosure system or kit; considerations which are not entirely satisfied by state of the art products. The roof assembly must be formed of relatively few component parts that are inexpensive to manufacture by conventional techniques. The roof assembly must also be capable of being packaged and shipped in a knocked-down state. In addition, the roof assembly must be modular and facilitate the creation of a family of roof assemblies that vary in size but which share common, interchangeable components.
Finally there are ergonomic needs that a roof assembly must satisfy to achieve acceptance by the end user. The roof assembly must be easily and quickly assembled using minimal hardware and requiring a minimal number of tools. In addition, the roof assembly must not require excessive strength to assemble or include heavy component parts. Moreover, the roof assembly must assemble together in such a way so as to not detract from the internal storage volume of the resulting enclosure or otherwise negatively affect the utility of the structure.